It is becoming more and more desirable that the performance of the power group, that is, an engine and transmission combination for vehicles must be developed from their present state in order to improve their utilisation of available fuel energy. Such a desirable development requires increased overall performance, increased efficiency of the transmission, better use of the engine in favourable ranges, adaptation of the transmission to allow design of the engine to produce output power as cheaply as possible with least variation of conditions under which the engine is used and, further, to enable a manufacturer to vary the composition of the transmission to suit the type of vehicle in question without losing sight of the main preferred features.
Another demand of future transmissions which is not satisfied by known transmissions is that economical driving conditions are automatically set according to specific demand for the vehicle and its use.
A further aim for a future transmission must be to reduce the demand for high quality and expensive materials and to reduce both the size of transmission and servicing as well as extending the trouble-free operation time of the vehicle.
The situation today is that automatic transmissions normally have higher fuel consumption for each ton-mile transport than the manually controlled synchromesh transmissions. The situation is also that the increased power of the vehicles has shortened the life of both engine and transmission and increased the servicing requirements. Generally speaking current transmissions are only suitable for a limited field of use or it is left to the ability of the driver to influence fuel consumption and the utilization of performance factors.